General: Remove usages of ARRAY_SIZE where applicable. (#5392)

Same behavior, but without our own boilerplate function.

src/video_core/renderer_opengl/gl_state.cpp

@@ -206,7 +206,7 @@ void OpenGLState::Apply() const {
     }
 
     // Textures
-    for (unsigned i = 0; i < ARRAY_SIZE(texture_units); ++i) {
+    for (u32 i = 0; i < texture_units.size(); ++i) {
         if (texture_units[i].texture_2d != cur_state.texture_units[i].texture_2d) {
             glActiveTexture(TextureUnits::PicaTexture(i).Enum());
             glBindTexture(GL_TEXTURE_2D, texture_units[i].texture_2d);

src/video_core/renderer_opengl/gl_state.h

@@ -90,10 +90,11 @@ public:
     GLenum logic_op; // GL_LOGIC_OP_MODE
 
     // 3 texture units - one for each that is used in PICA fragment shader emulation
-    struct {
+    struct TextureUnit {
         GLuint texture_2d; // GL_TEXTURE_BINDING_2D
         GLuint sampler;    // GL_SAMPLER_BINDING
-    } texture_units[3];
+    };
+    std::array<TextureUnit, 3> texture_units;
 
     struct {
         GLuint texture_cube; // GL_TEXTURE_BINDING_CUBE_MAP